The Gougeon Brothers on Boat Construction - WEST SYSTEM Epoxy

Chapter 14 – Hardware Bonding 149
Keelson
Floor timber
Keel
Stainless steel
pipe threaded on
outside and set
in epoxy filled hole
Keel bolt
Nut and washer set up on
head of keel bolt against
stainless steel pipe
Planking
Nut set up on keel
bolt against stainless
steel pipe. Epoxy
thickened with
404/406 (silica) in
gap at top of keel
Lead ballast keel
Figure 14-26 Cross section of a removable bonded keel.
Choose stainless pipe or tubing of sufficient inner
diameter to allow a keel bolt to pass through it. For
each bolt hole, cut a sleeve long enough to touch the
keel and protrude through the floors inside the boat.
A lead keel is soft, so position nuts on the keel bolts
before casting it, just flush or slightly above the lead.
<strong>The</strong>se will separate the keel and the hull. Slide the
pieces of threaded pipe over the keel bolts and firmly
fasten them with nuts. You may have to fabricate
temporary nuts that will pass through the holes in the
boat and hold the pipe firmly to the keel. Seal the
joint where the pipe meets the keel with thickened
epoxy. <strong>The</strong>n install the keel as described for bonded
keels. Lower the keel and saw off the excess pipe.
Install the keel using a good gasket material around
the keel bolt/pipe.
Bonding Through-Hull Fittings in Tubes
Rudder and propeller shafts, cockpit drains, and other
fittings often pass through the hull in tubes to protect
end-grain wood. <strong>The</strong>se tubes must be watertight, and
they must bond well, but they are not always easy to
obtain. We solve the problem by building piping for
the through-hull fittings with WEST SYSTEM epoxy and
fiberglass. <strong>The</strong>re are several ways to do this.
One very popular method is to find plastic tube or
metal rod of the right diameter and use it as a mold.
Make sure that the mold is clean and that it has no
nicks or scratches and coat it with paste auto wax or
another mold release.
Next, wet two layers of 4 oz (135 g/m2 ) woven fiberglass
cloth with epoxy and wrap them around the
mold. Let the epoxy cure. <strong>The</strong>n, using a sharp knife,
slice through the fiberglass along the length of the tube.
Break the glass free of the mold, but for the moment
leave it in place. <strong>The</strong> cut is necessary because the mold
may not be perfectly round; without it, it might be very
difficult to remove the finished tube. Wet out more
glass cloth and wrap it around the tube until you reach
the desired thickness. Some epoxy may seep into the
cut, but this will not create any problems. Remove the
fiberglass tubing from the mold when the epoxy has
cured.
With a slightly modified technique, aluminum tubing
may also be used as a mold. Coat the aluminum with
heat-resistant mold release—Teflon spray is a good
choice—and wrap fiberglass cloth and epoxy around it
as before. <strong>The</strong>n heat the tube to about 120°F (49°C)
with a hair dryer or heat gun. Keep it warm until the
epoxy cures.
As the aluminum heats, both it and the wet-out fiberglass
will expand. When it cools, it will shrink to original
size, but the fiberglass/epoxy tube will remain slightly
larger. This makes it possible to remove the new tube.
If you have trouble sliding the glass from the mold,
try pulling it off with pliers.
A variation on this second method can be used to
make good-fitting, low-speed bearings. Mix WEST
SYSTEM epoxy with 406 Colloidal Silica or 423 Graphite
Powder and apply it to a Teflon-coated aluminum tube.
Heat the tube until the thickened epoxy is fairly hard.
Wet out fiberglass cloth with epoxy, wrap it around the
tube and the adhesive mixture, and allow it to cure.
Allow the part to cool and pull it off with pliers.